The overall goal of this program project grant is earlier and more accurate diagnosis of neoplastic lesions by means of nuclear imaging. Project I is concerned with the development of novel modular scintillation cameras, which will offer advantages over conventional Anger cameras in terms of spatial resolution, count rate, and energy resolution. Project II is for continued research into various kinds of coded apertures for gamma-ray image formation. The emphasis here will be on obtaining true three-dimensional reconstructions. Specific research will be performed on reconstruction algorithms, hybrid digital-optical computers, the rotating slit aperture, the Fourier aperture, and multiple pinhole apertures. Project III involves the use of miniature hand held detector probes to achieve more accurate estimation of the extent of tumor at the time of surgery. The hypothesis to be tested is that intraoperative use of these probes can improve surgical oncological staging by identifying sites of neoplastic involvement that are not clinically evident. Project IV will explore some new ways to display 3D image data. Emphasis will be placed on an interactive CRT display in which the user can tune back and forth through the depth of the object. Project V comprises clinical and psychophysical evaluation of the new techniques being developed in the other projects.